title: Diffusion of small molecules into medaka embryos improved by electroporation.
abstract: BACKGROUND
  Diffusion of small molecules into fish embryos is essential for many experimental procedures in developmental biology and toxicology. Since we observed a weak uptake of lithium into medaka eggs we started a detailed analysis of its diffusion properties using small fluorescent molecules.
  
  
  RESULTS
  Contrary to our expectations, not the rigid outer chorion but instead membrane systems surrounding the embryo/yolk turned out to be the limiting factor for diffusion into medaka eggs. The consequence is a bi-phasic uptake of small molecules first reaching the pervitelline space with a diffusion half-time in the range of a few minutes. This is followed by a slow second phase (half-time in the range of several hours) during which accumulation in the embryo/yolk takes place. Treatment with detergents improved the uptake, but strongly affected the internal distribution of the molecules. Testing electroporation we could establish conditions to overcome the diffusion barrier. Applying this method to lithium chloride we observed anterior truncations in medaka embryos in agreement with its proposed activation of Wnt signalling.
  
  
  CONCLUSIONS
  The diffusion of small molecules into medaka embryos is slow, caused by membrane systems underneath the chorion. These results have important implications for pharmacologic/toxicologic techniques like the fish embryo test, which therefore require extended incubation times in order to reach sufficient concentrations in the embryos.
authors.affiliation: Department for Applied Life Sciences, University of Applied Sciences, FH Campus Wien, Helmut-Qualtinger-Gasse 2, A-1030 Vienna, Austria.
authors.forename: Gerlinde
authors.initials: G
authors.lastname: Jung
authors.forename: Markus
authors.initials: M
authors.lastname: Hug
authors.forename: Christian
authors.initials: C
authors.lastname: Halter
authors.forename: Andrea
authors.initials: A
authors.lastname: Friesenhengst
authors.forename: Johann
authors.initials: J
authors.lastname: Walzer
authors.forename: Thomas
authors.initials: T
authors.lastname: Czerny
mesh_terms: D000165:Acridine Orange / Q000493:pharmacokinetics; D000818:Animals; D002823:Chorion / Q000378:metabolism; D003902:Detergents / Q000493:pharmacokinetics; D004058:Diffusion; D018274:Electroporation; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D019793:Fluorescein / Q000493:pharmacokinetics*; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D008094:Lithium / Q000493:pharmacokinetics*; D009990:Oryzias / Q000196:embryology* / Q000378:metabolism*; D010063:Ovum / Q000378:metabolism; D012235:Rhodamines / Q000493:pharmacokinetics; D060449:Wnt Signaling Pathway
chemical_list: D003902:Detergents; D005456:Fluorescent Dyes; D012235:Rhodamines; D008094:Lithium; D000165:Acridine Orange; C029773:rhodamine B; D019793:Fluorescein